Sterility and shelf-life are important considerations in the manufacture of many liquid food products, such as liquid nutrition products and beverages. Food manufacturing practices must achieve final products with assured microbial safety, e.g., sterility. Traditionally, this means products must be heat processed to reduce any potential microbial contamination to meet or exceed the levels of sterility prescribed for such products in national and international legislation. In addition, products typically must be stored for extended periods of time and hence unstable components cannot be included without deterioration or must be over-dosed to ensure that minimal quantities remain at point of consumption. For many products, such as infant formulas and other liquid nutrition products, it is desirable that the products contain certain essential nutrients, such as all of the essential nutrients needed for human infant growth and development in the case of infant formula.
A prerequisite to an infant formula is that the final product must be microbiologically safe, and for that reason traditional processing mandates that the final product be adequately heat processed. Thus, products in liquid form are subject to a rigorous heat treatment typically by exposure to high temperatures for short time (UHT—aseptic process) or by retorting. The retort sterilization has been recommended for products used in hospitals to feed premature and term newborn babies.
While these thermal treatments can be successful in assuring microbial safety, they can adversely affect the molecular components and structures that are ingredients in infant formulas and other liquid nutrition products. Invariably, heat-treating complex infant formula mixtures leads to various reactions of individual molecules and to interactions between different components. One prior art strategy to resolve the losses caused by these destructive reactions with respect to the final quantities of components of formula is to include a sufficient excess of the ingredients as a quantitative function of the instability to ensure that sufficient levels of essential nutrients remain in the final product. The strategy of using excess nutrients prior to processing the formula ignores the potential implications to the user of consuming thermal reaction products formed during processing. Thus, although necessary, the thermal processing of nutritional components can generate compounds or intermediates that may have undesirable nutritional consequences.
Another drawback of thermal processing is that it can generate advanced glycation end products (AGEs). Through the Maillard reaction, certain amino acids such as lysine can react with aldehyde groups of glucose to first create Schiff bases and then rearrange to Amadori products. These reactions produce various glycoxidation and lipoxidation products which are collectively known as AGEs. AGEs are formed by the Maillard reaction during food processing when, for example, mixtures containing protein and carbohydrates are heated. However, AGEs also may be formed endogenously in the body and are thought to contribute to the natural aging process.
AGEs are end-products that in general retain little chemical reactivity. They are formed via complex chemical reactions which may include oxidation reactions and the formation of reactive intermediates. Thus, AGEs can be considered markers for the formation of these reactive intermediates. These intermediates include glyoxal, methylglyoxal, 3-deoxyglucosone, glyceraldehyde, and others. Examples of AGEs are lactuloselysine, hydroxymethylfurfural, oxalic acid monolysinylamide, and carboxymethyllysine.
It has been suggested that AGEs may be linked to chronic low level inflammation. This is due in part to oxidative stress caused by AGEs. Chronic low level inflammation has been linked to a number of diseases. For example, it is hypothesized that chronic low level inflammation may be linked to diabetes, cardiovascular disease, Alzheimer, cancer, and even weight gain and aging. A reduction in AGEs in the diet may lead to an extension of life span; prevention/reduction of weight gain; prevention of insulin resistance; prevention of heart disease; and improvement of oxidative stress. Many scientific papers have been written postulating links between AGEs and various disease states. One such paper is entitled “Advanced Glycation Endproducts” by Wauthier and Guillasseau, Diabetes Metab (Paris) 2001, 27, 535-542. See also International Patent Publication No. WO 2006/029298 A1 entitled “Nutritional Products Having Improved Quality And Methods And Systems Regarding Same”. The foregoing paper and published patent application are hereby incorporated by reference in their entireties as part of the present disclosure.
Typically, infant formula and other liquid nutrition products must be pre-processed to achieve the final composition and to uniformly disperse and solubilize all formula ingredients (proteins, carbohydrates, lipids and other nutrients) and to produce a homogenous emulsion. The emulsion is further processed by high pressure homogenizations and heating to assure homogeneity and reduce bacterial load. If a ready-to-feed liquid is desired, the emulsion is filled into appropriate packaging and subjected to a further heat treatment. The heat treatment may be applied either before filling in which case filling is carried out under aseptic conditions or the filled containers may themselves be heat treated in a retort process. In addition, some infant formulas are produced and packaged for the first feeding in hospitals. Many such hospital-targeted products are produced in ready-to-feed liquid form in small bottles called nursettes, and are sterilized in such containers by retort processing.
The majority of destructive reactions and of undesirable Maillard reactions that lead to various decomposition and polymerization products including AGEs occur when proteins, lipids and carbohydrates are heated in a liquid phase. This intensive heating is also a factor that leads to the decomposition of various heat labile nutrients. Once they begin during the heating process, many chemical reactions continue, although at slower reaction rates, throughout the storage of either liquid or dry products at room temperature. It should also be noted that under factory conditions it may be necessary for batches of liquid product to be kept in holding tanks at various stages in the manufacturing process for reasons such as unplanned work on necessary processing equipment. Any delays occurring in this way will increase the potential for AGE formation.
Formulations containing whey proteins, bioactive compounds and other nutritional components found in human milk can be necessary for infant formula, especially for low birth weight infants when feeding with human milk is not an option. The heat lability and reactivity of some of these components makes it particularly difficult to incorporate some of them into liquid formulas which are thermally sterilized. As indicated above, conventional thermal processes can result in nutrient degradation, loss of functionality, reduction of shelf-life and the development of unwanted by products. In order to improve the product quality it is necessary to produce the formula in a manner that minimizes the exposure of those components to excessive heating. Sterilizing such components using cold sterilization processes or less severe heat processes would allow the development of formulas with improved qualities and that more closely approximate human breast milk.
It is an object of the present invention to overcome one or more of the above-described drawbacks and/or disadvantages of the prior art.